#define _CRT_SECURE_NO_WARNINGS
#include"byy.h"
int main()
{
	double sinx = 0;
	double  t;
	double x;
	int n;
		scanf("%lf",&x);
		t = x;
		for (n=3; fabs(t)>=1e-7;n+=2)
		{
			sinx+= t;
			t = -t*(x*x) / (n * (n - 1));
		}
		printf("%lf", sinx);
	return 0;
}